Newsprint and similar materials are transported in large, massive rolls in which the sheet material is wound around a central cylindrical core of fibre or cardboard. Such objects are sufficiently heavy that they must be handled by crane for loading and unloading from vessels. They are readily damaged and so must be handled carefully in such loading and unloading. To facilitate loading and unloading such rolls, various core lifting chucks have been developed which have a probe which is inserted into the central cylindrical core of the roll and which grips the central core, to allow the roll to be lifted by a cable from a crane or the like.
The present inventor's U.S. Pat. No. 5,439,264 issued Aug. 8, 1995, entitled "Apparatus for Lifting Objects Having a Hollow Cylindrical Core" discloses a compact lifting probe which uses a single lifting cable attached to scissoring toggle arms, which can be readily removed from the roll core in case of jamming, is readily adjustable, and which is self-releasing when the load is to be released. It has a lower probe section which is inserted into the hollow core of the paper roll consisting of an inner component which is attached to a single lifting cable by means of the toggle arms, and an outer component which is attached to a horizontal plate against which the toggle arms act. When raised, the outer component is pressed downwardly. This causes a cone-shaped lower end of the inner component to force outwardly the ends of a number of pivoting fingers on the lower end of the outer component, which then engage and grip the inner core of the paper roll. When the roll is returned to the ground, the inner component drops back down, the fingers retract and the probe is removed from the core. Prior designs required two cables and two widely separated lifting arms, and so were cumbersome, heavy and unwieldy to operate, taking two persons to handle. The width of the two arms, which frequently swing around during the loading process, caused safety problems, and the two lines may become tangled.
One aspect of the present inventor's prior lifting probe is that it automatically releases from the core of the paper roll as soon as the roll is placed on a surface and the lifting pressure from the cable is released. In some situations that can be undesirable, since some adjustment or juggling of the paper rolls may be required by the crane operator after the roll has first been placed on a surface. It is preferable that the release of the probe can be made remotely at the discretion of the operator to avoid the danger of a worker in close proximity to the cable, lifting probe and paper roll. There is therefore a need for a lifting probe which can be released remotely from the paper roll.